perf tools: Remove poll.h and wait.h from util.h

Not needed in this header, added to the places that need poll(), wait()
and a few other prototypes.

Link: http://lkml.kernel.org/n/tip-i39c7b6xmo1vwd9wxp6fmkl0@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>